Changes in Effective Optical Zone After Small-Incision Lenticule Extraction in High Myopia

Purpose: To evaluate the four measurement approaches on the determination of effective optical zone (EOZ) using Scheimpflug tomography after SMILE surgery in eyes with high myopia.Setting: Corneal refractive surgery conducted in eye hospital in southern ChinaDesign: A retrospective cohort study.Methods: Total 74 subjects were recruited. EOZ was measured at 3 months postoperatively using Vertex-Based total corneal refraction method (EOZV), pupil-based total corneal refraction method (EOZP), 4 mm-Ring-Based total corneal refraction method (EOZ4), and axial curvature difference map (EOZD), and their consistencies were compared. EOZs and planned optical zone (POZ) were compared and analyzed with eccentricity, ablation degree (AD) and total corneal aberrations.Results: Mean AD was -6.87 ± 0.75 D, and eccentricity was 0.30 ± 0.17 mm. At 3 months after surgery, the mean root mean square of ΔHOA, ΔComa, ΔTrefoil and ΔSA were 0.53 ± 0.27 μm, 0.36 ± 0.20 μm, 0.01 ± 0.84 μm, and, 0.16 ± 0.14 μm respectively. EOZV, EOZP, EOZ4 and EOZD were 5.87 ± 0.44 mm, 5.85 ± 0.45 mm, 4.78 ± 0.40 mm, 5.29 ± 0.27 mm respectively, which were significantly smaller than POZ 6.48 ± 0.16 mm. Bland Altman plots showed a good consistency between the four EOZs. The difference between the EOZV and EOZP was 0.02 mm within the range of clinically acceptable difference. In addition, EOZD was positively correlated with AD, and the eccentricity was positively correlated with ΔHOA, ΔComa and ΔSA.Conclusions: All 4 measurement approaches demonstrated the reduction of EOZs compared to POZ. EOZV was the closest to POZ, followed by EOZP. ΔEOZs showed no significant difference with eccentricity, AD and corneal aberrations. Our results are useful for the full characterization of corneal treatment profiles after kerato-refractive surgery.

Reversal of Myopic Correction for Patients Intolerant to LASIK

Purpose. To evaluate the outcome of the reversal of myopia correction in patients intolerant to LASIK. Methods. This study is a retrospective and case series of patients who decided to reverse their previous myopic LASIK correction between July 2012 and July 2020. It was conducted at a private refractive surgery centre, Ismailia, Egypt. The patients were followed up after reversal treatment for one year. Primary LASIK and reversal treatment were performed by a 500 kHz Amaris excimer laser platform. The main outcomes included refractive predictability, stability, efficacy, and safety and any reported complications. Results. This study included 48 eyes of 24 patients (6 male and 18 female patients). The average duration between the primary LASIK surgery and reversal treatment was 3.20 ± 0.30 months (range 3 to 4 months). Reversal treatment was bilateral in all patients. The mean age of the patients was 38 ± 1.9 years (range 37 to 45 yrs). After reversal, the mean postreversal cycloplegic refraction spherical equivalent was −1.82 ± 0.34 D (range −1.50 to −3.00 D). The mean ablation depth was 34.10 ± 7.36 μm (range 20 to 46 μm), and the mean of the central corneal thickness 12 months after reversal treatment was 510.2 ± 14.4 μm (range 515 to 487 μm). The mean keratometric reading was 42.6 ± 1.6 (range 42.5 to 44.8). The mean of CDVA was 0.2 ± 0.03 log MAR (range −0.10 to 0.4 log MAR). The mean optical zone of reversal treatment was 6.1 ± 0.3 mm (range 5.9 to 6.2 mm). UDVA was 0.4 log MAR in 87.5% of the patients, 0.5 log MAR in 8.3% of the patients, and 0.6 log MAR in 4.2% of the patients. CDVA remained unchanged in 83.3% of patients; 2.1% of the patients gained one line of CDVA (Snellen); 8.3% of the patients lost one line of CDVA; 6.3% of the patients lost two lines of CDVA. No cases of corneal ectasia were recorded. The only postoperative complications were flap microfolds in 3 eyes (6.25%). Conclusion. In conclusion, this study demonstrates that reversal of myopic LASIK treatment is a safe, stable, and effective option for intolerant patients.

Analysis of Corneal Spherical Aberrations in Chinese Bilateral Ectopia Lentis Patients

Purpose: To analyze the anterior, posterior, and total corneal spherical aberrations (ASA, PSA, and TSA) in patients with Chinese bilateral ectopia lentis (EL).Methods: A cross-sectional study was conducted to evaluate corneal spherical aberration (CSA) using a Pentacam system at the 6-mm optical zone. Axial length, keratometry, astigmatism, and corneal asphericity were also determined.Results: This study included 247 patients (420 eyes) with a mean age of 18.1 years. The values of ASA, PSA, and TSA were 0.136 ± 0.100 μm, −0.118 ± 0.030 μm, and 0.095 ± 0.095 μm, respectively. In the EL patients with Marfan syndrome (MFS), ASA and TSA were significantly lower than in the non-MFS patients (0.126 ± 0.094 μm vs. 0.155 ± 0.107 μm, P = 0.004 for ASA; 0.085 ± 0.091 μm vs. 0.114 ± 0.099 μm, P = 0.003 for TSA), whereas PSA was not significantly different (P = 0.061). The values of ASA and TSA were significantly higher in the patients with EL aged ≥ 40 years old than in younger patients, whereas ASA and PSA were lower in patients aged <10 years old than in older patients (all P < 0.05). In the multiple linear regression analysis, age, keratometry, astigmatism, anterior asphericity, higher-order aberration (HOA), and lower-order aberration (LOA) were positively or negatively correlated with TSA in the patients with EL (r = 0.681, P < 0.001).Conclusions: Corneal spherical aberration was low in the patients with EL especially for MFS and tended to increase with aging. Preoperatively, individual measurement of CSA was necessary for bilateral EL patients with MFS.

Functional optical zone after wavefront-optimized versus wavefront-guided laser in situ keratomileusis

Background: Many studies have used functional optical zone (FOZ) as a measure to compare different refractive laser treatment modalities. However, to our knowledge, no study has compared wavefrontoptimized (WFO) and wavefront-guided (WFG) laser in situ keratomileusis (LASIK) using FOZ. We compared the FOZ after WFO versus WFG LASIK in patients with myopia and myopic astigmatism.Methods: In this prospective comparative study, we included 100 myopic eyes of 50 patients with or without astigmatism. They were divided into two groups according to the platform used: WFO or WFG femtosecond LASIK. Using Holladay’s equivalent keratometry reading (EKR) report of Pentacam HR, FOZ was defined as a zone centered on the pupil center with a standard deviation (SD) of 0.5 D, around the mean EKR. The differences in FOZ between the two platforms were analyzed at 3 months postoperatively. Visual acuity, refractive error, corneal asphericity (Q-value), and root mean square of higher-order aberrations (RMS for HOAs) were evaluated and compared.Results: The mean ± SD of patient age was 26.64 ± 5.67 years. The preoperative characteristics of the two groups were comparable (all P > 0.05). The intended optical zone (IOZ) was 6 mm in both groups. The mean laser ablation depth was significantly greater in the WFG group (18 ?m per D) than in the WFO group (16 ?m per D) (P = 0.035). At 3 months postoperatively, the mean ± SD of FOZ diameter was 4.32 ± 0.94 mm (71.99 ± 15.68% of intended optical zone) in the WFO group and 4.16 ± 1.13 mm (69.33 ± 18.78% of intended optical zone) in the WFG group, with no significant difference between the two groups (P = 0.622). The change in corneal asphericity was greater in the WFG group than in the WFO group (P = 0.034). Postoperative mean corrected and uncorrected distance visual acuity, manifest refraction, and RMS for HOAs showed no significant difference between the two groups (all P > 0.05).Conclusions: We found that WFG LASIK resulted in greater ablation depth and change in corneal asphericity than WFO LASIK at 3 months postoperatively. However, there was no significant difference in FOZ diameter, refractive error, and RMS for HOAs between the two groups. Further research is needed to confirm these findings.

Impact of Unintended Initial Dissection of the Posterior Plane on Surgery Time During Small Incision Lenticule Extraction Surgery

Background: To study the impact of unintended initial dissection of the posterior plane (UIDPP) on operation time and surgical outcomes during small incision lenticule extraction (SMILE) surgery.Methods: Based on the SMILE procedure video, the operating eyes were assigned to the normal and UIDPP groups according to the presence or absence of UIDPP signals during surgery. The UIDPP group was further separated into early and late detection. Patient's demographic data, preoperative evaluation data, operation time and postoperative outcomes were collected.Results: Sixty-six patients who underwent SMILE were included, with 24 patients with UIDPP (13 in the early detection group and 11 in the late group). The optical zone was smaller (median 6.5 vs. 6.6, P=0.007), and the operation time was longer (median, 189.5 vs. 91.0 s, P<0.001) in the UIDPP group compared with controls. There were significant differences in operation time between the late detection group and early detection group (median, 489.0 vs. 139.0 s, P<0.05) and between the late detection group and normal group (489.0 vs. 91.0 s, P<0.05), while the optical zone was different only between the late detection and normal groups (median, 6.6 vs. 6.5, P<0.05). Conclusion: The occurrence of UIDPP will increase the surgery time of SMILE. Detecting IUDPP earlier could help shorten the operation time.

Comparison of Early Visual Quality in Patients using Different Optical Zones Based on Dark Pupil Diameters in Small Incision Lenticule Extraction (SMILE)

AIM: The early visual qualities of patients were evaluated after small incision lenticule extraction (SMILE) using different optical zones based on dark pupil diameters.METHODS: A case-control study was conducted to include 49 myopic patients (96 eyes) who underwent SMILE surgery. Patients were divided into three groups according to the difference between the diameter of the optical zone and the diameter of the dark pupil: Group A (<0 mm, N=30), Group B (0-1 mm, N=36), and Group C (>1 mm, N=30). In all groups, the dark pupil diameter was measured preoperatively. Subjective visual quality, uncorrected vision acuity (UCVA), spherical equivalent (SE), modulation transfer function cut-off frequency (MTFcutoff), objective scattering index (OSI), simulated contrast visual acuity (VA100%, VA20%, VA9%), total corneal higher-order aberration (tot-HOA), corneal spherical aberration (totZ40) and corneal coma (tot-coma) were measured preoperatively and 3 months postoperatively. P< 0.05 was considered statistically significant.RESULTS: There were no statistically significant differences in age, sex, UCVA, SE, corneal higher-order aberration, OQAS or subjective visual quality among the three groups before surgery (P>0.05). At 3 months postoperatively, there was no significant difference in UCVA, SE, MTFcutoff, OSI, VA100%, VA20%, or VA9% among the three groups (P>0.05). However, the tot-HOA, totZ40 and tot-coma indexes and the changes in corneal higher-order aberrations (Dtot-HOA, DtotZ40, Dtot-coma) at 3 months postoperatively were as follows: Group A > Group B > Group C (P<0.05). At 3 months postoperatively, the difference in subjective visual quality between the three groups was statistically significant (P<0.05). The difference in the amount of change in subjective visual quality between Groups A and C was statistically significant (P<0.05).CONCLUSION: Although the difference between the diameter of the optical zone and the diameter of the dark pupil does not affect the VA or the same diopter of patients after SMILE myopia correction, the optical zone diameter should be greater than the dark pupil diameter as far as possible in the design of SMILE surgery, in order to improve the objective visual quality and subjective satisfaction of patients after surgery.

Comparison of 6.0 mm versus 6.5 mm Optical Zone on Visual Outcomes after LASIK

Previous studies have demonstrated safety and efficacy using 6.0 and 6.5 mm optical zones in the WaveLight EX500 Excimer Laser System but have not evaluated if differing optical zone sizes influence refractive outcomes. This study examines visual outcomes between two study populations undergoing LASIK with either a 6.0 mm (1332 patients) or 6.5 mm (1332 patients) optical zone. Outcomes were further stratified by severity of myopia (low, moderate, and high) and astigmatism (low and high). Patients were matched by age and preoperative manifest sphere and cylinder. Postoperative measurements were then compared. The 6.5 mm group demonstrated better postoperative manifest refractive spherical equivalent (MRSE), manifest sphere, and absolute value of the difference in actual and target spherical equivalent refraction (|∆ SEQ|), within the total population, moderate myopia, and low astigmatism groups, but this did not lead to improved postoperative uncorrected distance visual acuity (UDVA) or best corrected distance visual acuity (CDVA). Though astigmatic correction and postoperative angle of error were similar between optical zone sizes, they were significantly worse with high myopia. Overall, this study demonstrates differences in visual outcomes between the 6.0 and 6.5 mm optical zone sizes that may warrant consideration; however, essentially, the results are comparable between them.

Comparison of Refractive and Visual Outcomes after Transepithelial Photorefractive Keratectomy (TransPRK) in Low versus Moderate Myopia

Is it possible to obtain good results in myopia of 2 or fewer diopters (D) with transepithelial photorefractive keratectomy (TransPRK) changing the optical zone and epithelium thickness? We retrospectively analyzed two groups of 296 eyes with a minimum follow-up of 4 months. Group A had 2 or less D, treated with an optical zone (OZ) 0.2 mm bigger than recommended, and a central epithelium thickness of 60 microns, and group B had 2 D to 5 D, with the recommended optical zone, and a 55-micron epithelium ablation at the center. The outcomes were not different between the two myopic ranges; the postop uncorrected distance visual acuity was 20/20 ± 4 in both groups (p = 0.2), which was −0.3 ± 0.8 lines worse than the preoperative corrected distance visual acuity in both groups (p = 0.5). The safety of the treatments resulted in a change of 0.0 ± 0.7 lines in the low myopia group, versus a gain of +0.1 ± 0.8 lines in the moderate myopia group (p = 0.1). The deviation from the intended target was −0.04 ± 0.33 D in the low myopia group and +0.07 ± 0.32 D in the moderate myopia group (p < 0.0001); the postoperative spherical equivalent was 0.00 ± 0.33 D in the low myopia group and +0.10 ± 0.31 D in the moderate myopia group (p < 0.0001). The postop refractive astigmatism was 0.32 ± 0.16 D in both groups (p = 0.5). In conclusion, the refractive and visual outcomes after TransPRK are comparable in low myopia changing the optical zone and epithelium thickness versus moderate myopia with standard optical zone and epithelium thickness.

Clinical case of congenital abnormality of the iris floccula eye vasculature

Purpose. Description of a clinical case of an iris floccule in a girl of 17 years old. Material and methods. 17-year-old patient who complained about a decrease in vision of the right eye and a change in the shape of the pupil. she was examined by visimetry, biomicroscopy, tonometry, ophthalmoscopy. 3 years ago she was consulted at the ophthalmology center, where there was revealed lysoriness and changes in the eyes. No surgical or laser treatment has been proposed. Changes in the area of pupil's parents noticed in early childhood, in the last 3 years the changes increased. Result. The patient was assigned midriatics, to open the optical zone and improve visual acuity, recommended consultation to resolve the issue of surgical or laser removal of brush-shaped floccules to eliminate obscuration and prevent amblyopia. Conclusion. Clinical case indicates that timely surgical treatment is necessary to achieve results. Treatment should be carried out as soon as possible, since vision loss is a high-risk area for the development of obscurative amblyopia. Key words: iris flocculi, vascular abnormalities.